Measures of infant social behavior in several situations and several settings were made at one year of age. We are studying the relationships among these measures in order to address the conceptual issue of what are the most appropriate behavioral measures of mother-infant attachment. As part of this effort we are also studying reactions to strangers. The sample was evenly divided with respect to sex and birth order, thus allowing us to study both sex and birth order differences. In addition to methodological questions, we plan to examine the antecedents of the distinctive tie between mother and infant. Approximately half the sample was observed at six months as part of Project Z01.HD00002-04. Several of the environmental variables observed at that time have been hypothesized to relate to later attachment, e.g., amount of kinesthetic stimulation and mother's responsiveness to baby's distress. BIBLIOGRAPHIC REFERENCES: Klein, R. P. and Durfee, J. T. Infants' reaction to unfamiliar adults versus mothers. Child Development, 1976, 47, 1194-1196.